I haven't seen yet what the value of $file is before that code is executed. Add some prints to help debug, like:

print "Start: \$file = $file\n";
my($thebase) = ($file =~ /(.*)\/[^\/]+/);
print "  \$thebase = $thebase\n";

my($html,$html2);

print "Just before test to see if \$file exists\n";
if (!-e $file){
   print "$file does *NOT* exist!\n";
   $thebase =~ s/\/[^\/]+$/\/default/;
   print "\$thebase *AFTER* substituting default = $thebase\n";

    ### the rest of your code ###
[download]

Those will help figure out exactly what your code is doing. Once we see the results of that it will be easier to offer help.